The Devil You Know
by Deranged Silence
Summary: Yuichiro Hyakuya. The wielder of a Black Demon Series cursed blade. Possessed by a demon. When said demon takes the time to properly influence her host, Yu can hardly wait to try out his newfound abilities. Features a stronger Yu, a female Asuramaru (explained inside) and a (hopefully) enjoyable story, I present to you, "The Devil You Know".


"This is starting to become a little _too_ familiar, Yu." The voice of his demon, Asuramaru, still contained that strange, echoing quality that had always drawn Yuichiro Hyakuya to her. It was very difficult to describe. Often, he had heard her voice in his dreams. She whispered stories of demons and vampires, and recently, of the angels of Heaven. Asuramaru did not like the angels. To be honest, even without his – Yu supposed the best word to describe it would be _possession_ – first and only interaction with the angels, Yu would be wary of them still; the way his demon's voice would waver. "You said that we are friends, yes?"

They were in that clouded place once again. It seemed that the only time Asuramaru would let him see her was here. "We are friends, Asuramaru." Yu frowned up at the girl, her long purple hair moving of its own accord – she frowned back down at him. He was on the ground, which was new for his experiences here. Asuramaru was sitting on his lap, it seemed. How or why, he did not know. "What is your point?"

"What is it friends do?"

Yu answered her without hesitation. "They protect each other." Was that the answer she was looking for? Yu had never seen the demon look so serious before. Asuramaru had always been a lot like Shinoa. They both teased him constantly and were almost never seen without a smile on their faces.

Although, since Asuramaru was a demon, it would be Shinoa who was more like Asuramaru, just by fact of age. Even so, Yu had known Shinoa the longest. Does age define who is like who, or was it the time spent with them?

"Save your pondering for another time, Yu," the demon admonished with her lips tilted into a smirk. "Friends protect each other, hmm? That's what you're telling me?"

Nodding, Yu's frown deepened.

"That is why I give you power to protect your friends and your family?" Her finger pressed against the tip of his nose, the dainty little digit pushing it this way and that as her eyes watched the wave of red spread across his cheeks. Humans. "Then what do you give me out of this deal?"

"I- We're friends! Isn't that what we agreed upon?" It was what they had said. Every night since they deepened their bond, Asuramaru hadn't said anything more about it. She hadn't teased him about the unfairness of the bargain they struck, or even how he never had much time to spend with her. "Are you upset with the deal? Is that why you dragged me here?"

The demon laughed, somehow making it so the sound came from everywhere but her lips. "I didn't bring you here, Yu. But, let's say that was the reason. What would you do?"

"I would change the deal."

Asuramaru smiled down at him and Yu heard an ethereal giggle echo in his mind. His demon was being extremely playful, now. "I don't want a different deal. Not entirely. I like being friends with you."

Yu was absolutely confused right now. "Then what-"

"You are too weak to protect me, Yu. That is what I am saying. There is no human, past, present or future, that has the power to protect a demon."

"Asuramaru, that's why I borrow your power."

Her eyes gleamed as she tilted her head. Yu knew that look. This was what she was waiting for him to say. "The slightest portion of my power, plus a mortal body makes you stronger than a demon, then?" Asuramaru shifted her weight on his lap, reminding him of their position. His eyes were drawn away from where her white dress pooled at his waist to the way the light shone on the tips of her canine teeth, slightly enlarged as they were, poking out from her upper lip. "You don't deserve my power, Yu."

She must have enjoyed the way Yu froze beneath her, either at the slim hands that she was snaking up her chest or her words, as they hit him like a spray of unnaturally cold blood. Maybe it was both that caused Yu to stiffen. He remained frozen in place as her thin arms wound their way around his neck, her face brought close to his own. "You, Yuichiro Hyakuya, deserve your own power. Will you become a demon, as well as an angel?"

"For the power to keep my family whole? For the right to protect you and my friends?" Yu let the tension slip away from his body at her words. "Damn right I will."

"Well then, Yu. I suppose it is a good thing you died when you did." Asuramaru giggled once more before her lips found his own, and his vision turned to darkness.

 **So… At the start of this fanfic, I believed Asuramaru to be a girl. Yeah, laugh all you want. I saw subbed before I saw the dubbed, and was totally blindsided. So, this is going to be slightly more AU then I expected. Don't blame me, blame the trap of watching anime. Besides, apparently a lot of people mad the same mistake I did. Some are even saying that Asuramaru, like all the demons, can choose their form at will. I don't really hold with that theory, but this is really just me saving face. So, to be clear, Asuramaru is female in this fic. No, I haven't read the manga, but I plan to, it just won't have an impact on where this story is going.**


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